What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

O-320H2AD Engine perfomance interpretation help

WingnutWick

Well Known Member
Looking for help to interpret some engine performance data on a friend's O-320H2AD to determine if the motor is under performing or the prop is pitched more towards a cruise prop. It is a Catto prop and from my understanding you should be able to hit 2700 RPM in flight wide open if all things are correct and you're using an all around prop.

Here is the data:

TAKEOFF: OAT-90 230’

Starting at 750 RPM - smooth but quick application to full throttle: 2100 RPM @ 3 seconds, 2200 RPM in 6 seconds, 2300 @12 seconds and hovers around 2330 RPM through lift off.

IN FLIGHT PERFORMANCE:
5500: OAT- 85 / RPM- 2600 / MAP-24.7 / IAS:161 MPH (140 KTS)

7500: OAT- 76 / RPM- 2560 / MAP- 22.8 / IAS:150 MPH (130 KTS)

10500: OAT- 64 / RPM- 2480 / MAP-20.3 / IAS- 137 (119 KTS)

Thank you for the help!
CW
 
Impossible to accurately determine SHP from your data but the first guess would be you are indeed over-propped. Assuming your flight numbers are WOT, the RPM appears low there and at static. The contradicting data to me would be lower rpm with increasing DA. Lower DA data would be helpful to see if RPM trend reverses at some lower altitude.

Got a prop manual for it? If it is adjustable pitch, I'd set it for minimum static RPM and repeat your data gathering.
 
I have the same engine and a Catto prop. My guess is slightly over pitched, but I would talk to Catto. They know their stuff better than anybody!
 
I should be able to help you out.
I have a Catto, and an (I) O-320-H2AD

First thing, I need TAS not IAS. If you don't have a Dynon or something that calculates TAS, then we need actual GS on a 3 leg course. NTPS spreadsheet, search for that here...

Also we need to standardize altitude. Always 7500' Density Altitude. That is the 75% power at WOT point.
Lean appropriately to max power, as consistently as is possible. Have an advanced engine monitor?

Standardize weight. Two on board? It will be slower.

It could be you have drag issues that are slowing down the plane... once solved it will go faster and be a more suitable prop. But I agree, right now it looks like too much pitch. But lets not jump to conclusions too fast.

Mine is a 68 x 69 repitched to 71". I hit (even exceed) 2700 at WOT, solo, half tanks, 7500' DA.
 
Last edited:
Check throttle

Are you sure the throttle is opening to the stop on the carb?
Might want to check that.
 
Back
Top